In the late and much lamented HBO sketch series Mr. Show, there's a running gag in which a slick music industry type surprises a man singing to himself in the bathroom mirror, triumphantly declaring that he's "got the goods." The show then quickly cuts to a dream-come-true montage in which the newly minted superstar climbs to the top of the charts, his success illustrated with a cheap cut-out of a graphic handily labelled "Song Chart."

It's a silly bit of comedy, but I couldn't help but return to it, again and again, while watching the new Tupac Shakur biopic, All Eyez on Me.

Shakur lived a life of ambition, excess, and boundless creativity. Any filmmaker taking on his life story would be spoiled for choice as to how to present and dissect his myriad accomplishments (five massive albums, six hit movies, countless controversies, all before he was shot dead at 25).

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Yet, in All Eyez on Me, director Benny Boom chooses what might best be called the Mr. Show approach: It is 140 minutes of people telling Shakur that he's indeed "got the goods." We hear it from his manager, Atron Gregory (Keith Robinson). We hear it from nameless record executives. We hear it from such famous Shakur friends as Jada Pinkett (Kat Graham), Dr. Dre (Harold House Moore) and Biggie Smalls (Jamal Woolard, again playing the rapper after 2009's Notorious).

And then we get to witness Shakur's name literally climb the charts, thanks to a barrage of "Song Chart" graphics and that ol' hackneyed standby, the spinning newspaper.

What we don't get, and what Boom seems uninterested in, is any insight into Shakur's craft, the passions or demons that drove him, or anything that defined him as an artist, as a crusader for social justice, as anything beyond a caricature designed for a quick Mr. Show-esque comedy sketch.

Shakur is a name that continues to echo throughout cultural history, but to Boom, that's all he is: a name. All Eyez on Me's Tupac Shakur is a cipher, an easy way for its producers to assemble a by-the-numbers biopic that trades on the worst clichés of the hip-hop world (that is, drugs, bling and a preoccupation with women's butts that puts the Fast and Furious franchise to shame).

Spoiling Shakur's legacy is one thing – plenty of musician biopics have squandered can't-miss opportunities; I'm looking at you, Get on Up and Beyond the Sea – but All Eyez on Me is doubly disappointing in that it also wastes the considerable talents of its leading man. Demetrius Shipp Jr. is blessed with an uncanny resemblance to Shakur, and he's lived most of his adult life being told so: he first auditioned for the role in 2011, before the film fell into development hell.

Boom and his producers should consider themselves fantastically lucky that Shipp stuck around for the past six years, as the novice actor possesses an undeniable magnetism.

A half-smile is enough to disarm, and a close-up of his eyes more than enough to convey the weight of Shakur's lyrical, tortured soul.

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Yet the direction of music-video vet Boom never allows Shipp to shine, and a hammy script by a trio of writers keeps Shakur firmly planted in one of two modes: smooth-talking mama's boy or abrasive hothead. Shipp frequently tries to inch away from the raw deal he's been handed, but the movie's thudding obviousness always keeps him frozen in place, at the mercy of filmmakers uninterested in anything other than exploiting a cultural icon.

Boom's indifference eventually crosses over into gross irresponsibility, as when the film chronicles Shakur's 1993 sex-assault case, in which he was convicted of first-degree sexual abuse. There is surely a humane, sensitive way to investigate such a toxic chapter in Shakur's life, but the director and his screenwriters instead paint the most nauseating portrait of Shakur's accuser possible, alternately depicting her as a sex fiend or a mess of hysterics.

It's all the more queasy given how the film otherwise divides women into angels (Shakur's activist mother, loving fiancée Kidada Jones, the supportive Pinkett) or sex objects (everyone else).

By the time that courtroom chapter unfolds, though, it wasn't too shocking to see how Boom would handle such a matter.

Up until that point, he'd already confirmed All Eyez on Me as a cheap, lazy exercise in myth-making. The goods, as it were, will have to be found elsewhere.